The invention relates to an optical projection device comprising a light source and a lens plate integrator which comprises a first lens plate having a predeterminable number of lens elements and arranged in the optical path between the light source and a projection plane, and a second lens plate having a predeterminable number of lens elements and arranged in the optical path between the first lens plate and the projection plane. Light from the light source is imaged by means of the lens elements of the first lens plate on the lens elements of the second lens plate associated with the lens elements of the first lens plate, and the light beams of the lens elements of the second lens plate superimposed on the projection plane by means of a prismatic arrangement of the lens elements of the second lens plate or by means of a condenser lens.
In such optical projection devices, a very uniform illumination of a projection face in the projection plane is achieved by means of the lens plate integrator which comprises at least two lens plates each having a predeterminable number of lens elements. This means that the light on the projection face has a very homogeneous intensity distribution, i.e. particularly the light distribution in the center area and the peripheral areas of the projection face is substantially the same. Such optical projection devices including a lens plate integrator have the additional advantages that the light distribution on the projection plane or on the projection faces is quite insensitive to small variations of the position of the light source. Moreover, the device is insensitive to mechanical tolerances of the overall system. It is also insensitive to inhomogeneities of the light source itself, which may be caused, for example, by faults in the reflector, by electric wires, etc. Furthermore, the projection face is illuminated in homogeneous colors.
An optical projection device of this type is known, for example, from U.S. Pat. No. 5,418,583. In this device, the second lens plate of the lens plate integrator comprises additional lens elements of different sizes. The lens elements arranged at the periphery of the second lens plate are slightly smaller than those arranged in the center area so as to allow for the differently sized image of the light source on the lens elements of the second lens plate. In any case, this device also has for its object that each light beam passed through the lens elements of the second lens plate is imaged on the projection plane in a maximally uniform way and completely covers a projection face on this plane.